Numerical characterization of inter-core coalescence by AC dielectrophoresis in double-emulsion droplets.

The utilization of an alternating current electric field provides a good means to achieve controlled coalescence between paired inner cores encapsulated in water-in-oil-in-water double-emulsion (DE) droplets. Although previous studies have experimentally determined the conditions under which inter-core electrokinetic fusion occurs, the transient interfacial dielectrophoretic (DEP) dynamics key to understand the underlying fluid mechanics is still unclear from a physical point of view. By coupling DEP motion of two-phase flow to phase-field formulation, bulk-coupled numerical simulations are conducted to characterize the spatial-temporal evolution of the surface charge wave and the resulting nonlinear electrical force induced at both the core/shell and medium/shell oil/water interfaces. The effect of interfacial charge relaxation and droplet geometry on inter-core attractive dipolar interaction is investigated within a wide parametric space, and four distinct device operation modes, including normal inter-core fusion, shell elongation, partial core leakage, and complete core release, are well distinguished from one another by flow regime argumentation. Our results herein reveal for the first time the hitherto unknown transient electrohydrodynamic fluid motion of DE droplet driven by Maxwell-Wagner structural polarization. The dynamic simulation method proposed in present study points out an effective outlet to predict the nonlinear electrokinetic behavior of multicore DE droplets for realizing a more controlled triggering of microscale reactions for a wide range of applications in drug discovery, skin care, and food industry.

Numerical investigation of field-effect control on hybrid electrokinetics for continuous and position-tunable nanoparticle concentration in microfluidics.

We introduce herein an effective way for continuous delivery and position-switchable trapping of nanoparticles via field-effect control on hybrid electrokinetics (HEK). Flow field-effect transistor exploiting HEK delicately combines horizontal linear electroosmosis and transversal nonlinear electroosmosis of a shiftable flow stagnation line (FSL) on gate terminals under DC-biased AC forcing. The microfluidic nanoparticle concentrator proposed herein makes use of a simple device geometry, in which an individual or a series of planar metal strips serving as gate electrode (GE) are subjected to a hybrid gate voltage signal and arranged in parallel between a pair of 3D driving electrodes. On the application of a DC-biased AC electric field across channel length direction, all the GE are electrochemically polarized, and the action of imposed hybrid electric field on the multiple-frequency bipolar counterions within the composite-induced double layer generates two counter-rotating induced-charge electroosmotic (ICEO) micro-vortices on top of each GE. Symmetry breaking in ICEO flow profile occurs once the gate voltage deviates from natural floating potential of corresponding GE. The gate voltage offset not only results in an additional pump motion of working fluid for enhanced electroosmotic transport but also directly changes the location of FSL where nanoparticles are preferentially collected by field-effect HEK. Our results of field-effect control on HEK are supposed to guide an elaborate design of flexible electrokinetic frameworks embedding coplanar metal strips for a high degree of freedom analyte manipulation in modern micro-total-analytical systems.

DC electric field-driven heartbeat phenomenon of gallium-based liquid metal on a floating electrode.

The heart beating phenomenon of room temperature liquid metal (LM) mercury has attracted much attention in the past years, but its research and application are limited because of the low vapor pressure and high toxicity. Here, a fundamental scientific finding is reported that the non-toxic eutectic gallium indium (EGaIn) alloy droplets beat periodically at a certain frequency based on a floating electrode under the stimulation of the direct current (DC) field. The essential characteristics of heart beating are the displacement and the projected area change of the LM droplet. The mechanism of this phenomenon is the self-regulation of interfacial tension caused by chemical oxidation, chemical corrosion, and continuous electrowetting. In this article, a series of experiments are also carried out to examine the effects of different factors on the heartbeat, such as voltage, the volume of the droplet, the droplet immersion depth, the electrolyte solution concentration, the distance of electrodes, and the type of floating electrode. Finally, the heartbeat state and application boundary of the LM droplet under different conditions are summarized by imitating the human life process. The periodic changes of the LM droplet under an external DC electric field provide a new method to simulate the beating of the heart artificially, and can be applied to the research of organ chip fluid pumping in the future.

Process of Glucose Increases Rather Than Constant High Glucose Was the Main Cause of Abnormal Glucose Induced Glomerulus Epithelial Cells Inflammatory Response.

Abnormal glycemia is frequently along with nephritis, whose pathogenesis is unexplicit. Here, we investigated the effects of abnormal glucose on the renal glomerulus epithelial cells by stimulating immortalized bovine renal glomerulus epithelial (MDBK) cells with five different levels of glucose, including low glucose (2.5 mM for 48 h, LG), normal glucose (5 mM for 48 h, NG), high glucose (25 mM for 48 h, HG), increasing glucose (24 h of 2.5 mM glucose followed by 24 h of 25 mM, IG), and reducing glucose (24 h of 25 mM glucose followed by 24 h of 2.5 mM, RG). The results showed that LG and RG treatments had nonsignificant effects (p > 0.05) on the viability of MDBK cells. HG treatment decreased the viabilities of cells (p < 0.01) without triggering an apparent inflammatory response by activating the nox4/ROS/p53/caspase-3-mediated apoptosis pathway. IG treatment decreased the viabilities of cells significantly (p < 0.01) with high levels of pro-inflammatory cytokines IL-1ß and IL-18 in the supernatant (p < 0.05) by triggering the txnip/nlrp3/gsdmd-mediated pyroptosis pathway. These results indicated that the process of glucose increase rather than the constant high glucose was the main cause of abnormal glucose-induced MDBK cell inflammatory death, prompting that the process of glycemia increases might be mainly responsible for the nephritis in diabetic nephropathy, underlining the importance of glycemic control in diabetes patients.

Continuous-Flow Nanoparticle Trapping Driven by Hybrid Electrokinetics in Microfluidics.

We introduce herein an efficient microfluidic approach for continuous transport and localized collection of nanoparticles via hybrid electrokinetics, which delicately combines linear and nonlinear electrokinetics driven by a composite DC-biased AC voltage signal. The proposed technique utilizes a simple geometrical structure, in which one or a series of metal strips serving as floating electrode (FE) are attached to the substrate surface and arranged in parallel between a pair of coplanar driving electrodes (DE) in a straight microchannel. On application of a DC-biased AC electric field across the channel, nanoparticles can be transported continuously by DC bulk electroosmotic flow, and then trapped selectively onto the metal strips due to AC-field induced-charge electrokinetic (ICEK) phenomenon, which behaves as counter-rotating micro-vortices around the ideally polarizable surfaces of FE. Finite-element simulation is carried out by coupling the dual-frequency electric field, flow field and sample mass transfer in sequence, for guiding a practical design of the microfluidic nanoparticle concentrator. With the optimal device geometry, the actual performance of the technique is investigated with respect to DC bias, AC voltage amplitude, and field frequency by using both latex nanospheres (∼500 nm) and BSA molecules (∼10 nm). Our experimental observation indicates nanoparticles are always enriched into a narrow bright band on the surface of each FE, and a horizontal concentration gradient even emerges in the presence of multiple metal strips, which therefore permits localized analyte enrichment. The proposed trapping method is supposed to guide an elaborate design of flexible electrokinetic frameworks embedding FE for continuous-flow analyte manipulation in modern microfluidic systems.

Pumping of electrolyte with mobile liquid metal droplets driven by continuous electrowetting: A full-scaled simulation study considering surface-coupled electrocapillary two-phase flow.

With the excellent merits of both solid conductors and rheological fluids, liquid metal (LM) provides new opportunities to serve as flexible building blocks of miniaturized electronic and fluidic devices. The phenomenon of continuous electrowetting (CEW) has been long utilized for actuating LM contents in buffer medium, wherein an externally imposed voltage difference is responsible of manipulating the interfacial tension of deformable LM droplets. CEW effectively lowers the surface tension at the LM/electrolyte interface by driving bipolar counterions to the surface of conducting droplet. Since surface tension coefficient relies sensitively on the local voltage drop across the induced double layer, an electric-analogy Marangoni effect occurs even under a rather weak electric field in the presence of a surface gradient of the interfacial tension. CEW of LM routinely induces unidirectional pumping of electrolyte in the direction of applied electric field, with LM droplet translating oppositely within the device channel. Although this subject has received great attention from the microfluidic society in the past decade, previous reports concerned either the individual delivery of the suspension medium or the transport of LM droplet. Starting from this point, we offer herein a fully coupled physical description of two-phase flow dynamics occurring in CEW. The proposed simulation model successfully incorporates the synergy of the interfacial electrokinetic momentum transfer, surface tension on a curved surface, contact angle at the three-phase contact line as well as the gravity force density. The spatial-temporal motion of the contact interface is traced instantly with a moving mesh approach. By direct numerical simulation, the importance of the direct-current bias, additional alternating-current forcing, droplet size, initial ion adsorption in the process of CEW is addressed. Additionally, it is discovered that increasing the number of LM droplet is more cost-effective than enhancing the volume of a single drop in terms of achieving an improvement of the resulted electrocapillary pump performance, while the translational speed of the discrete droplet carrier does not make an observable change in response to a variation in the drop number. These results prove invaluable in terms of an elaborate design of smart on-chip electrokinetic frameworks embedding flexible LM contents in modern micro-total-analytical systems.

Secukinumab-induced multiple lentigines in areas of resolved psoriatic plaques: A case report and literature review.

Psoriasis is a systemic inflammatory disease commonly associated with postinflammatory hyper- and hypo-pigmentation. Psoriasis-related cytokines such as IL-17 and TNF can contribute to these pigmentation changes by regulating both the growth and pigment production of melanocytes. Here, we present the first reported the case of a patient with a 10-year history of severe psoriasis vulgaris, who developed multiple lentigines in areas of resolved psoriatic plaques during anti-IL-17A antibody secukinumab.

On ion transport regulation with field-effect nonlinear electroosmosis control in microfluidics embedding an ion-selective medium.

We study herein numerically the use of induced-charge electrokinetic phenomena to enable a flexible control of ion transport of dilute electrolyte in a straight ion concentration polarization system. The effect of three convection modes of induced-charge electrokinetic phenomena, including induced-charge electroosmosis, flow-field effect transistor, and alternating-current electroosmosis (ACEO), on convective arrestment of diffusive wave-front propagation is investigated by developing a cross-scale and fully coupled transient numerical simulation model, wherein multiple frequency electrochemical polarization and nonlinear diffuse charge dynamics in spatiotemporally varying solution conductivity are taken into account. We demonstrate by detailed comparative simulation studies that ACEO vortex flow field above a metal strip array arranged along the anodic chamber's bottom surface serves as the most efficient way for adjusting the salt density distribution at micrometer and even millimeter dimension, due to its high flexibility in controlling the stirring flow state with the introduction of two extra electrical parameters. The specific operating status is determined by whether the electrode array is floating in potential (induced-charge electroosmosis) or biased to ground (flow-field effect transistor) or forced to oscillate at another Fourier mode (ACEO). These results prove useful for on-chip electric current control with electroconvective stirring.

Efficient Micro/Nanoparticle Concentration using Direct Current-Induced Thermal Buoyancy Convection for Multiple Liquid Media.

Thermal-based microparticle focusing has recently received increasing attention due to its noninvasive nature and simple manipulation mechanism. However, its further application is limited by current complicated fluid heating systems and low particle focusing velocity. Using simple indium tin oxide-made microheaters, herein we propose a flexible and novel approach for efficient particle focusing based on direct current-induced thermal buoyancy convection. Importantly, for avoiding possible electrochemical reactions on the electrode, the microheaters are isolated from the granular fluids of interest by a thin glass slide. The concentration performance of the designed chip was first demonstrated by statically focusing 4-µm silica particles, yeast cells, silica particles in insulating buffer, and 100-nm copper microspheres. Also the trapping of a mixture of 5-µm and 2-µm polystyrene microbeads indicated that the chip can either simultaneously concentrate two kinds of particles or selectively focus the heavier ones by adjusting the voltages. Then the different concentration patterns of microbeads exhibited that the microspheres can be flexibly manipulated by changing the configurations of microheaters. Furthermore, for the first time, we achieved thermal-based continuous particle focusing in both conducting and insulating solutions using buoyancy convection, demonstrating that this method can be utilized to achieve both static and continuous particle manipulations in multiple liquid media. Finally, the feasibility of this device in effective wear measurement of machines was demonstrated by conducting systematic experiments of focusing nanocopper particles in the hydraulic oil. Therefore, this presented approach would be promising for a broad range of on-chip applications.

Continuous Particle Trapping, Switching, and Sorting Utilizing a Combination of Dielectrophoresis and Alternating Current Electrothermal Flow.

We propose a simplified multifunctional traffic control approach that effectively combines dielectrophoresis (DEP) and alternating current electrothermal (ACET) flow to realize continuous particle trapping, switching, and sorting. In the designed microsystem, the combined DEP and ACET effects, which are symmetrically generated above a bipolar electrode surface, contribute to focus the incoming colloidal particles into a thin beam. Once the bipolar electrode is energized with an electric gate signal completely in phase with the driving alternating current (AC) signal, the spatial symmetry of the electric field can be artificially reordered by adjusting the gate voltage through field-effect traffic control. This results in a reshapable field stagnant region for precise switching of particles into the region of interest. Moreover, the integrated particle switching prior to the scaled particle trapping experiment is successfully conducted to demonstrate the feasibility of the combined strategy. Furthermore, a mixture of two types of particle sorting (i.e., density, size) with quick response performance is achieved by increasing the driving voltage with a maximum gate voltage offset, thus, extending the versatility of the designed device. Finally, droplet switching and filtration of the satellite droplets from the parent droplets is performed to successfully permit control of the droplet traffic. The proposed traffic control approach provides a promising technique for flexible manipulation of particulate samples and can be conveniently integrated with other micro/nanofluidic components into a complete functional on-chip platform owing to its simple geometric structure, easy operation, and multifunctionality.

Compound-Droplet-Pairs-Filled Hydrogel Microfiber for Electric-Field-Induced Selective Release.

The separate co-encapsulation and selective controlled release of multiple encapsulants in a predetermined sequence has potentially important applications for drug delivery and tissue engineering. However, the selective controlled release of distinct contents upon one triggering event for most existing microcarriers still remains challenging. Here, novel microfluidic fabrication of compound-droplet-pairs-filled hydrogel microfibers (C-Fibers) is presented for two-step selective controlled release under AC electric field. The parallel arranged compound droplets enable the separate co-encapsulation of distinct contents in a single microfiber, and the release sequence is guaranteed by the discrepancy of the shell thickness or core conductivity of the encapsulated droplets. This is demonstrated by using a high-frequency electric field to trigger the first burst release of droplets with higher conductivity or thinner shell, followed by the second release of the other droplets under low-frequency electric field. The reported C-Fibers provide novel multidelivery system for a wide range of applications that require controlled release of multiple ingredients in a prescribed sequence.

A microscopic physical description of electrothermal-induced flow for control of ion current transport in microfluidics interfacing nanofluidics.

The phenomenon of electrothermal (ET) convection has recently captured great attention for transporting fluidic samples in microchannels embedding simple electrode structures. In the classical model of ET-induced flow, a conductivity gradient of buffer medium is supposed to arise from temperature-dependent electrophoretic mobility of ionic species under uniform salt concentrations, so it may not work well in the presence of evident concentration perturbation within the background electrolyte. To solve this problem, we develop herein a microscopic physical description of ET streaming by fully coupling a set of Poisson-Nernst-Planck-Navier-Stokes equations and temperature-dependent fluid physicochemical properties. A comparative study on a standard electrokinetic micropump exploiting asymmetric electrode arrays indicates that, our microscopic model always predicts a lower ET pump flow rate than the classical macroscopic model even with trivial temperature elevation in the liquid. Considering a continuity of total current density in liquids of inhomogeneous polarizability, a moderate degree of fluctuation in ion concentrations on top of the electrode array is enough to exert a significant influence on the induction of free ionic charges, rendering the enhanced numerical treatment much closer to realistic experimental measurement. Then, by placing a pair of thin-film resistive heaters on the bottom of an anodic channel interfacing a cation-exchange medium, we further provide a vivid demonstration of the enhanced model's feasibility in accurately resolving the combined Coulomb force due to the coexistence of an extended space charge layer and smeared interfacial polarizations in an externally-imposed temperature gradient, while this is impossible with conventional linear approximation. This leads to a reliable method to achieve a flexible regulation on spatial-temporal evolution of ion-depletion layer by electroconvective mixing. These results provide useful insights into ET-based flexible control of micro/nanoscale solid entities in modern micro-total-analytical systems.

On hybrid electroosmotic kinetics for field-effect-reconfigurable nanoparticle trapping in a four-terminal spiral microelectrode array.

Induced-charge electroosmosis (ICEO) has attracted tremendous popularity for driving fluid motion from the microfluidic community since the last decade, while less attention has been paid to ICEO-based nanoparticle manipulation. We propose herein a unique concept of hybrid electroosmotic kinetics (HEK) in terms of bi-phase ICEO (BICEO) actuated in a four-terminal spiral electrode array, for effective electrokinetic enrichment of fluorescent polystyrene nanoparticles on ideally polarizable metal strips. First, by alternating the applied AC voltage waves between consecutive discrete terminals, the flow stagnation lines where the sample nanoparticles aggregate can be switched in time between two different distribution modes. Second, we innovatively introduce the idea of AC field-effect flow control on BICEO; by altering the combination of gating voltage sequence, not only the number of circulative particle trapping lines is doubled, but the collecting locations can be flexibly reconfigured as well. Third, hydrodynamic streaming of DC-biased BICEO is tested in our device design, wherein the global linear electroosmosis dominates BICEO contributed from both AC and DC components, resulting in a reduction of particle enrichment area, while with a sharp increase in sample transport speed inside the bulk phase. The flow field associated with HEK is predicted using a linear asymptotic analysis under Debye-Huckel limit, with the simulation results in qualitative agreement with in-lab observations of nanoparticle trapping by exploiting a series of improved ICEO techniques. This work provides an affordable and field-deployable platform for real-time nanoparticle trapping in the context of dilute electrolyte.

Modulation effect of vaginal mucosal microflora and susceptibility to Neisseria gonorrhoeae infections: a systematic review and meta-analysis.

OBJECTIVE: The vaginal microbiota may modulate susceptibility to Neisseria gonorrhea (NG) infections. The objective of this meta-analysis was to evaluate the association between these NG infections and the vaginal microbiota. METHOD: A systematic review and meta-analysis was conducted to investigate the correlation of vaginal microbiota and NG risk. Primary sources of the reviewed studies were from inception through December 2018. Vaginal mucosa microflora were dichotomized into high-Lactobacillus vaginal microbiota and low-Lactobacillus vaginal microbiota (LL-VMB), using either Nugent score, Amsel's criteria, presence of clue cells or 16S rRNA gene sequencing. RESULTS: A total of 8 studies qualified for inclusion in this meta-analysis. LL-VMB could be regarded as worse prognostic factor, and the pooled OR was 1.33 (95% CI 1.02, 1.73; P = 0.04, I2 = 44%). LL-VMB was associated with a significantly higher susceptibility of NG. Trend for the sensitive analysis was consistence with the primary outcome. Significant publication bias was not detected by the funnel plot. CONCLUSION: In conclusion, the systematic review and meta-analysis has demonstrated that LL-VMB was significantly associated with a high NG susceptibility.

Flexible Continuous Particle Beam Switching via External-Field-Reconfigurable Asymmetric Induced-Charge Electroosmosis.

Continuous sample switching is an essential process for developing an integrated platform incorporating multiple functionality with applications typically ranging from chemical to biological assays. Herein we propose a unique method of external-field-reconfigurable symmetry breaking in induced-charge electroosmosis above a simple planar bipolar electrode for continuous particle beam switching. In the proposed system, the spatial symmetry of a nonlinear electroosmotic vortex flow can be artificially reordered to achieve an asymmetric electrically floating-electrode polarization by regulating the configurations of the external ac signals, thus contributing to flexible particle beam switching. This switching system comprises an upstream flow-focusing region where particles are prefocused into a beam on the bipolar electrode by transversal electroconvective mass transfer, and a deflecting region in which the resulting particle beam is deflected to generate a steerable lateral displacement to enter the desired region via the action of an asymmetric polarization-induced reshapable electroosmotic flow stagnation line in a controllable background field gradient. A lateral particle displacement on the order of hundreds of micrometers can be achieved in a deterministic manner by varying the voltage, frequency, and inlet flow rate, thereby enabling multichannel particle switching. Furthermore, the versatility of the switching mechanism is extended by successfully accomplishing fluorescent nanoparticle beam switching, yeast cell switching, five-outlet particle switching, and simultaneous switching of two particle types. The proposed switching approach provides a promising technique for flexible electrokinetic sample preconcentration prior to any subsequent analysis and can be conveniently integrated with other micro/nanofluidic components into a complete functional on-chip platform owing to its simple electrode structure.

Simulation analysis of rectifying microfluidic mixing with field-effect-tunable electrothermal induced flow.

We report herein field-effect control on in-phase electrothermal streaming from a theoretical point of view, a phenomenon termed "alternating-current electrothermal-flow field effect transistor" (ACET-FFET), in the context of a new technology for handing analytes in microfluidics. Field-effect control through a gate terminal endows ACET-FFET the ability to generate arbitrary symmetry breaking in the transverse vortex flow pattern, which makes it attractive for mixing microfluidic samples. A computational model is developed to study the feasibility of this new microfluidic device design for micromixing. The influence of various parameters on developing an efficient mixer is investigated, and an integrated layout of discrete electrode array is suggested for achieving high-throughput mixing. Our physical demonstration with field-effect electrothermal flow control using a simple electrode structure proves invaluable for designing active micromixers for modern micro total analytical system.

Flexible particle flow-focusing in microchannel driven by droplet-directed induced-charge electroosmosis.

We report herein a novel microfluidic particle concentrator that utilizes constriction microchannels to enhance the flow-focusing performance of induced-charge electroosmosis (ICEO), where viscous hemi-spherical oil droplets are embedded within the mainchannel to form deformable converging-diverging constriction structures. The constriction region between symmetric oil droplets partially coated on the electrode strips can improve the focusing performance by inducing a granular wake flow area at the diverging channel, which makes almost all of the scattered sample particles trapped within a narrow stream on the floating electrode. Another asymmetric droplet pair arranged near the outlets can further direct the trajectory of focused particle stream to one specified outlet port depending on the symmetry breaking in the shape of opposing phase interfaces. By fully exploiting rectification properties of induced-charge electrokinetic phenomena at immiscible water/oil interfaces of tunable geometry, the expected function of continuous and switchable flow-focusing is demonstrated by preconcentrating both inorganic silica particles and biological yeast cells. Physical mechanisms responsible for particle focusing and locus deflection in the droplet-assisted concentrentor are analyzed in detail, and simulation results are in good accordance with experimental observations. Our work provides new routes to construct flexible electrokinetic framework for preprocessing on-chip biological samples before performing subsequent analysis.

NF-E2-Related Factor 2 Suppresses Intestinal Fibrosis by Inhibiting Reactive Oxygen Species-Dependent TGF-ß1/SMADs Pathway.

BACKGROUND AND AIMS: This study aimed to evaluate the antifibrotic effects of NF-E2-Related Factor 2 (Nrf2) on intestinal fibrosis. Intestinal fibrosis is a common complication of Crohn's disease; however, its mechanism of intestinal fibrosis is largely unclear. METHODS: BALB/c mice received 2,4,6-trinitrobenzene sulfonic acid weekly via intrarectal injections to induce chronic fibrotic colitis. They also diet containing received 1% (w/w) tert-butylhydroquinone (tBHQ), which is an agonist of Nrf2. Human intestinal fibroblasts (CCD-18Co cells) were pretreated with tBHQ or si-Nrf2 followed by stimulation with transforming growth factor-ß1 (TGF-ß1), which transformed the cells into myofibroblasts. The main fibrosis markers such as α-smooth muscle actin, collagen I, tissue inhibitor of metalloproteinase-1, and TGF-ß1/SMADs signaling pathway were detected by quantitative real-time RT-PCR, immunohistochemical analysis, and Western blot analysis. Levels of cellular reactive oxygen species (ROS) were detected by dichlorodihydrofluorescein diacetate. RESULTS: tBHQ suppressed the intestinal fibrosis through the TGF-ß1/SMADs signaling pathway in TNBS-induced colitis and CCD-18Co cells. Moreover, Nrf2 knockdown enhanced the TGF-ß1-induced differentiation of CCD-18Co cells. ROS significantly increased in TGF-ß1-stimulated CCD-18Co cells. Pretreatment with H2O2, the primary component of ROS, was demonstrated to block the effect of tBHQ on reducing the expression of TGF-ß1. Moreover, scavenging ROS by N-acetyl cysteine could inhibit the increasing expression of TGF-ß1 promoted by Nrf2 knockdown. CONCLUSIONS: The results suggested that Nrf2 suppressed intestinal fibrosis by inhibiting ROS/TGF-ß1/SMADs pathway in vivo and in vitro.

BST2 promotes cell proliferation, migration and induces NF-κB activation in gastric cancer.

OBJECTIVES: To investigate the functional roles of bone marrow stromal cell antigen 2 (BST2) in gastric cancer (GC) cells and its implications in the development of GC patients. RESULTS: BST2 was frequently overexpressed in GC tissues compared with the adjacent non-tumorous tissues, and high BST2 expression was correlated with tumor stage and lymphatic metastasis. Furthermore, in vitro experiments demonstrated that knockdown of BST2 by siRNA inhibited cell proliferation, induced apoptosis and repressed cell motility in GC cells. In addition, the pro-tumor function of BST2 in GC was mediated partly through the NF-κB signaling. CONCLUSION: BST2 possesses the oncogenic potential in GC by regulating the proliferation, apoptosis, and migratory ability of GC cells, thereby BST2 could be a potential therapeutic target for the treatment of GC.

A Simplified Microfluidic Device for Particle Separation with Two Consecutive Steps: Induced Charge Electro-osmotic Prefocusing and Dielectrophoretic Separation.

Continuous dielectrophoretic separation is recognized as a powerful technique for a large number of applications including early stage cancer diagnosis, water quality analysis, and stem-cell-based therapy. Generally, the prefocusing of a particle mixture into a stream is an essential process to ensure all particles are subjected to the same electric field geometry in the separation region. However, accomplishing this focusing process either requires hydrodynamic squeezing, which requires an encumbering peripheral system and a complicated operation to drive and control the fluid motion, or depends on dielectrophoretic forces, which are highly sensitive to the dielectric characterization of particles. An alternative focusing technique, induced charge electro-osmosis (ICEO), has been demonstrated to be effective in focusing an incoming mixture into a particle stream as well as nonselective regarding the particles of interest. Encouraged by these aspects, we propose a hybrid method for microparticle separation based on a delicate combination of ICEO focusing and dielectrophoretic deflection. This method involves two steps: focusing the mixture into a thin particle stream via ICEO vortex flow and separating the particles of differing dielectic properties through dielectrophoresis. To demonstrate the feasibility of the method proposed, we designed and fabricated a microfluidic chip and separated a mixture consisting of yeast cells and silica particles with an efficiency exceeding 96%. This method has good potential for flexible integration into other microfluidic chips in the future.